Remote and automatic control mechanisms allow for increased productivity and enhanced safety in many industrial applications. For example, remote or automatic controlled valves may be used to control the flow of hot process fluids and high pressure steam in many industrial and commercial applications. These remote and automatic controllers eliminate the prior need for workers to open and close such flow control valves, thereby removing the possibility of human error, reducing the number of employees needed to operate complex fluid transfer systems, and reducing the possibility that a worker may become injured if a leak or malfunction may occur with the hot process fluid.
Early remote controlled valves still in use today in many applications utilize a solenoid driven linear actuator to open and close the valves to control the flow of fluid therethrough. The control for such solenoid valves is typically centrally located with power lines being run to each of the solenoids at each of the control valve locations. These valves typically only provide on/off control of the valves.
To provide variable flow control, the position of the valve stem has to be precisely controlled.
Such actuators utilize electrical control signals to cause an electric motor to operate, through either gears or a rack and pinion mechanism, to control the valve to open, close, or partially open positions. This allows the valve to control the flow of hot processed fluid, or steam, by way of remotely generated control signals of various magnitudes.
However, in installations that handle hot process fluid or steam, a considerable amount of heat from the process fluid or steam is conducted from the valve stem to the actuator assembly. Unfortunately, increased heat detrimentally affects the magnetics of the solenoid control mechanism as well as plastic gears and enclosures. As a result, precise control of the valve stem position is difficult. This results from the fact that additional energization current must be supplied to the solenoid as the temperature of the solenoid is increased by this thermal transfer. This precise control problem is exacerbated by the various installation locations and the impedance of the power lines from the central control to each individual solenoid controlled valve location. Likewise, as with the solenoid controlled valves, the increase in heat conducted from the valve stem to the actuator adversely affects the motor's ability to operate at a controlled level.
More modern remote and automatic controlled valves include the control electronics at the controlled valve location. Such design overcomes the problems associated with trying to precisely control valve stem position in a widely distributed fluid process control system from a centralized location. While the on-board electronics greatly enhance a valve's ability to precisely control the flow rate therethrough, electronics' inability to withstand high temperature environments has limited their applicability to process control systems for high temperature process fluids and steam. That is, when valves are used to control hot process fluids or steam, a considerable amount of heat is transferred through the valve stem to the actuator. This is because the moveable portion of the actuator mechanism must be rigidly connected to the valve stem to cause the valve to operate properly. Such heat transfer can be detrimental to sensitive components within the actuator, such as the control circuit electronics, the actuator motor, plastic gears, and the enclosure.
Therefore, there exists a need in the art for a thermal isolator that rigidly connects a valve actuator to the valve and that will allow proper operation of the actuator/valve combination while preventing unwanted heat from being transferred from the valve into the actuator mechanism.